The present invention relates to wheeled platforms and wheeled vehicles in general, and in particular, relates to apparatus, configurations and methods for providing highly mobile wheeled platforms suitable for a variety of uses, including, but not limited to, robotic devices.
The application of robotic devices and general-purpose transport platforms has enjoyed enormous growth in recent years, across all sectors of industrial, military and consumer/household operations, for a range of tasks limited only by the imagination of those employing such devices. These have included such disparate applications as surveillance, bomb disposal, industrial maintenance and household chores. In response to these demands, a number of configurations have been developed to provide enhanced mobility vehicle structures that can be used in transport and robotic device applications over rough surfaces or terrain. Representative examples of such configurations are disclosed in the following U.S. Pat. Nos.:
6,144,180
5,833,248
5,742,975
5,579,857
5,515,934
5,507,358
5,323,867
4,993,912
4,932,491
By way of example, U.S. Pat. No. 6,144,180 discloses a robot having a body, a pair of lift arms mounted pivotally on the body, a pair of leg support arms mounted pivotally on the lift arms, and a pair of wheeled leg assemblies mounted pivotally on each of the leg support arms. Each of the leg support arms is rotatable to turn one of the wheeled leg assemblies, which rests on the ground at the back of the other one of the wheeled leg assemblies, to a position in front of the other one of the wheeled leg assemblies, thereby moving forward the robot body. The lift arms can be rotated upward or downward relative to the leg support arms to lift or lower the robot body.
U.S. Pat. No. 5,833,248 purports to show a stairway ascending/descending vehicle that can ascend or descend stair-steps having a height greater than the diameter of the vehicle""s wheels. The vehicle has mainshafts rotatably supported on a front portion and a rear portion of a vehicle body, respectively. Front arm members are mounted to the front mainshafts; rear arm members are mounted to the rear mainshaft; and the front and rear arm members are configured to rotate with respect to the mainshafts.
U.S. Pat. No. 5,742,975 discloses an articulated vehicle for scrubbing floor surfaces defined by intersecting aisles of relatively narrow width. The vehicle has articulated portions that facilitate turns in narrow aisles.
U.S. Pat. Nos. 5,579,857 and 5,507,358 disclose stair-climbing vehicles having a body, front and rear wheels provided at the front and rear of the vehicle body, respectively, front and rear auxiliary wheels for lifting the front and rear wheels, respectively, by one stair-step, a driving unit for driving each wheel, a pivoting unit for pivoting the front and rear auxiliary wheels, sensors for detecting a riser portion of stairs, and a control unit for controlling the driving unit and the rotating unit in accordance with outputs of the sensors. It is claimed that since the vehicle ascends/descends stairs by rotation of the auxiliary wheels, a comer portion of the step of stairs is not damaged while the vehicle goes up and down stairs.
U.S. Pat. No. 5,515,934 discloses a modular robot body assembly segmented into five modules, symmetrically located around a horizontal center shaft system, enabling the robot body, front legs, and back legs to rotate about a horizontal center axis with respect to one another.
U.S. Pat. No. 5,323,867 discloses a robot transport platform adapted for locomotion, having a base with three wheels on each side. The wheels near the fore and aft ends are omnidirectional in design, while the intermediate wheel (between the omnidirectional wheels) is a conventional wheel. The omnidirectional wheels have staggered rows of spherical rollers rotatably mounted to the circumference of the wheel""s hub. Torque is provided by two electric motors independently operating the wheels on each side, and is transferred to the wheels via a gear box, a chain, and cogged drive belts.
U.S. Pat. No. 4,993,912 discloses a stair climbing robot having a chassis with powered, opposed front wheels and two pairs of rear wheels, each pair being rotatably mounted on a beam at opposite ends thereof, and each beam being rotatably mounted on the chassis. A drive motor is provided for driving each pair of wheels in the same direction at a predetermined rotational velocity; and a drive means is provided for simultaneously rotating the beams at a predetermined rotational velocity and in a predetermined direction. In operation, the beams rotate forward while each pair of rear wheels rotates in an opposite direction at the same rotational velocity. Forward movement is thus powered by the front wheels and rotating beams, while the rotational velocity of the rear wheels relative to the terrain is zero.
U.S. Pat. No. 4,932,491 describes a vehicle having auxiliary wheels that can be deployed to avoid overturning the vehicle when turning, traversing a slope, climbing an embankment or the like, and to right the vehicle when it is overturned.
Although the above-described devices represent advances over previous designs, wheeled platforms and devices such as those disclosed in the above-listed U.S. patents have notable limitations. They are typically inefficient, complex, cumbersome, heavy, and poorly suited to high-mobility operations on rough terrain or surfaces, such as traversing steep slopes, maneuvering around obstacles, and ascending or descending ramps or stairs.
Accordingly, there exists a need for wheeled platforms better suited to high-mobility, high-agility applications on rugged terrain and steep pitches. Ideally, such structures would be relatively robust, reliable, and conservative of battery or other energy sources, while providing enhanced abilities to traverse challenging terrain, and in some instances, to ascend or descend stairs and other obstacles. It is also desirable that such platforms be relatively compact, but scalable by selection of components and overall dimensions to adapt to various expected (and unexpected) terrain requirements.
The present invention provides wheeled platforms characterized by high mobility and reliability, which are readily used in a wide range of applications including transport and robotic devices. The wheeled platforms described herein can be operated on rough or steep terrain or surfaces; can ascend and descend conventional (and non-standard) stairs, whether indoors or outdoors; and can climb steep pitches smoothly. On stairs, the disclosed platforms can climb and descend with a minimum of step-induced dynamics, such as heave, pitch, and roll.
In addition, the disclosed platforms can turn-in-place (with a turning circle coextensive with the platform), are efficient, conservative of energy usage, and relatively simple in construction, and thus relatively inexpensive and lightweight.
The wheeled platforms described herein can be scaled (by component selection and overall dimension) so as to pass through standard doorways, crawl under standard furniture, and ensure low power consumption. In such embodiments, the wheeled platforms can include motive elements (whether electric, internal combustion or other) so that the platforms can propel themselves on level, uneven, or hilly ground, or over thresholds; and can maneuver on level terrain or on stairs, turning or changing direction as needed or directed.
A feature of the disclosed platforms is their ability to climb stairs with a rise per step on the same order of dimension as the diameter of a wheel element.
A number of overall configurations of wheeled platforms are disclosed herein. In a first configuration, a plurality of wheels are arrayed on either side of a body or base element, with wheel diameter and wheel spacing (or axle spacing) selected to enable the platform to traverse terrain elements, including stairs.
In another configuration, the wheeled platform is equipped with an articulated tail element that can be controlled to make selective contact with terrain.
In yet another configuration, the platform is articulated for relative movement of a first, forward body portion (referred to as a xe2x80x9cflipperxe2x80x9d) and second, rearward body portion (referred to as a xe2x80x9cbasexe2x80x9d) about a substantially horizontal axis of rotation. The flipper can be controlled to make selective contact with terrain.
In each of these configurations, wheel spacing can be selected to provide fore/aft overlap of the wheel elements; selective rocker of the wheels can be provided to facilitate turning-in-place and efficient movement over level terrain; independent port and starboard drives can be provided to enable maneuvers, turns, or turns-in-place; and intermediate wheel elements (in plan view) can be mounted outwardmost, to enable turning-in-place in limited spaces. In addition, deeply studded or scalloped wheel elements can be employed at selected wheel locations, to facilitate gripping of stair-steps.
Thus, in one aspect, the invention can be embodied in a wheeled structure in which first and second sets of wheel elements are rotatably attached, respectively, to first and second portions of a platform or body, wherein a portion of at least one wheel element overlaps a portion of at least one other wheel element in the same set of wheel elements. This overlap (which in one embodiment can be termed xe2x80x9cfore/aft overlapxe2x80x9d) can be further defined in that each wheel element has a defined radius (which need not be equal for all wheel elements), and a portion of at least one wheel element in a set of wheel elements overlaps another wheel element by a predetermined fraction of the radius of the other wheel element. In other words, the spacing between at least two wheel element axes will be less than the sum of the respective radii of the wheel elements. In an embodiment having equal-sized overlapping wheel elements (a constraint that is not required to practice the invention) the distance between the axes of one wheel element and another wheel element on the same side of the platform will be less than the diameter of the wheel elements. The wheeled structure thus defined can have 2, 3, 4, 5 or more axles, with 4, 6, 8 or more wheel elements (or even, in some embodiments, an odd number of wheel elements).
In another aspect of the invention, at least one of the intermediate wheel elements on each side of the wheeled structure (whether there are one or more intermediate wheels per side) are displaced outwardly from a longitudinal centerline of the body by an amount greater than that of any end wheel element. In other words, in plan view, the centermost wheel or wheels elements have a wider xe2x80x9ctrackxe2x80x9d than the end wheel elementsxe2x80x94i.e., the port-side and starboard-side center wheels, in plan view, are displaced outwardly from the body, relative to other wheels in the respective first and second sets of wheel elements. This increases the stability of the wheeled platform, while enabling the platform to turn-in-place within a circle defined by the radii of the outer corners of the platform.
It will be noted that in the following detailed description and in the claims, the term xe2x80x9cat least one intermediate wheel elementxe2x80x9d is used to denote one, two, three or more wheels per side (port and starboard or left and right) that are longitudinally between xe2x80x9couterxe2x80x9d or xe2x80x9ccornerxe2x80x9d wheel elements. Similarly, the outboard or corner wheel elements can number four or more. In an embodiment having four wheels, selected wheel elements can be arbitrarily designated as intermediate wheel elements. As the wheeled platform of the instant invention has no single direction of travel, the designations of left and right (in the viewer perspective) or port and starboard (in the coordinate system of the predominate direction of travel) are arbitrary and merely denote opposite sides of the body.
In one aspect of the invention, a selected degree of rocker is provided, such that the point of contact of the centermost wheel element on each side of the body can be lower than the respective point of contact of the end wheel elements. This facilitates the wheeled platform spinning or turning-in-place, thereby increasing agility. It will be understood by one of skill in the art that while in one embodiment, rocker of the wheel arrangement permits only one or two wheel-element pairs to contact a ground plane, in an alternate embodiment, the point of contact can be coplanar for all the wheels, depending on the weighting of the platform.
In another aspect of the invention, the body of the wheeled platform includes first and second body portions (which in one embodiment are fore and aft body portions), wherein the first body portion is connected to the second body portion via an articulation joint. The joint can be a hinge, pivot, or flexible body portion. The axis of articulation of the element can be substantially horizontal. The articulation element enables one of the body portions to act as a flipper having selective (and controllable) contact with the terrain, so as to increase the stability of the vehicle when traversing rugged terrain or climbing or descending stairs. In one embodiment, wheels are rotatably coupled to the flipper, and the flipper can provide support to the body (or other portion of the body) when traversing difficult or steep terrain or stairs. Angle control or motion control elements can be provided to control the angle of the flipper portion relative to the body (or other portion of the body).
In a further aspect of the invention, drive elements are provided to drive the wheel elements. In one embodiment, an independent drive element is arranged to drive at least one respective wheel element, and control elements are provided for controlling rotation of the respective wheel elements, to enable forward or reverse platform movement, turns or turns-in-place. In one embodiment, a first set of wheel elements is coupled to a port side of the body, a second set of wheel elements is coupled to a starboard side of the body, and independent port-side and starboard-side drive elements are provided to enable forward and rearward movement, turns or turns-in-place. In another aspect of the invention, the wheel elements in selected sets (or subsets) of wheel elements (e.g., left or right, port or starboard) can be geared or otherwise mechanically coupled so that the wheels in a wheel set turn in unison.
The wheel elements utilized in connection with the invention can include a tread portion; and in turn, the tread portion can be either smooth or patterned (e.g., with a studded or scalloped pattern). In other embodiments, wheel elements can be smooth or patterned with studded or scalloped patterns (without a distinct or separable tread portion). One such pattern thus consists of raised, spaced apart blocks. Another practice of the invention utilizes scalloped wheel elements at the corners of the platform (assuming more than 4 wheels) and smooth wheel elements for at least one of centermost wheel elements on each side. This facilitates turn-in-place, while maintaining the terrain-handling advantages (e.g., stair-climbing) afforded by scalloped wheel elements.
Finally, in the case of platforms useful in stair-climbing and descending, it has been found that the selection of wheel element diameter, axle count and axle spacing can and should be made in accordance with particular mathematical functions set forth hereinafter.
In alternative embodiments of the invention, fore/aft wheel element overlap is not utilized, but instead, wheel element diameter, wheel spacing, platform-to-wheel spatial displacement, and in one embodiment, flipper dimensions, are selected such that the platform is sufficiently high to avoid contact with obstacles or terrain elements, such as stairs. In particular, the wheels in this embodiment are disposed sufficiently close together (but without overlap) such that the vehicle can transverse stairs, rocks, thresholds or other obstacles (in some instances, by employing a flipper element), while maintaining the platform at a sufficient ground clearance to avoid ground/obstacle contact.
Additional features of the invention, its nature and various advantages are shown and described in the accompanying drawings and written description. The written description and attached drawing figures present the invention at various levels of enabling detail, from conceptual to specific examples of implementation. It will be appreciated by those skilled in the art that the present invention may be practiced in connection with details that differ from the specific examples of implementation set forth herein. By way of example, those skilled in the art will appreciate that the methods, systems and devices described herein can be implemented in devices, systems and methods differing from those depicted or described herein, and that the examples set forth herein are provided by way of illustration rather than limitation. In other instances, conventional or otherwise well-known structures and devices are described by way of reference to known or conventional engineering terminology.